Ozone-depleting chemicals decreasing in atmosphere, but weather plays big role in year-to-year variability

Staff Report

FRISCO — The ozone hole over Antarctica didn’t change much from last year, scientists said this week, pointing to weather and climate variability as key factors in year-to-year variability.

The single-day maximum area was similar to that in 2013, which reached 9.3 million square miles. The largest single-day ozone hole ever recorded by satellite was 11.5 million square miles) on Sept. 9, 2000. Overall, the 2014 ozone hole is smaller than the large holes of the 1998–2006 period, and is comparable to 2010, 2012, and 2013. Continue reading →

NASA’s Aeronomy of Ice in the Mesosphere, or AIM, mission captured this image of noctilucent clouds over the poles in 2010. By compiling data from several missions at once, researchers have now created a record of the clouds at lower latitudes as well. Image Credit: NASA/AIM

FRISCO — If you’ve been seeing more strange clouds that glow at night, it’s not your imagination. The occurrence of those types of clouds increased between 2002 and 2011, according to a new study analyzing satellite data from a variety of sources. Combining the information and using computer models, the NASA scientists found the greatest increase in areas between 40 and 50 degrees north latitude, a region which covers the northern third of the United Sates and the lowest parts of Canada. The research was published online in the Journal of Geophysical Research: Atmospheres on March 18, 2014.

These changes correlate to a decrease in temperature at the peak height where noctilucent clouds exist in the atmosphere. Temperatures at this height do not match temperatures at lower levels – indeed, the coldest place in the atmosphere is at this height during summertime over the poles – but a change there certainly does raise questions about change in the overall climate system.

“Noctilucent clouds occur at altitudes of 50 miles above the surface — so high that they can reflect light from the sun back down to Earth,” said James Russell, an atmospheric and planetary scientist at Hampton University in Hampton, Va., and first author on the paper. “AIM and other research has shown that in order for the clouds to form, three things are needed: very cold temperatures, water vapor and meteoric dust. The meteoric dust provides sites that the water vapor can cling to until the cold temperatures cause water ice to form.”

To study long-term changes in noctilucent clouds, Russell and his colleagues used historical temperature and water vapor records and a validated model to translate this data into information on the presence of the clouds. They used temperature data from 2002 to 2011 from NASA’s Thermosphere Ionosphere Mesosphere Energetics and Dynamics, or TIMED, mission and water vapor data from NASA’s Aura mission from 2005 to 2011. They used a model previously developed by Mark Hervig, a co-author on the paper at GATS, Inc., in Driggs, Idaho.

The team tested the model by comparing its output to observations from the Osiris instrument on the Swedish Odin satellite, which launched in 2001, and the SHIMMER instrument on the U.S. Department of Defense STPSat-1 mission, both of which observed low level noctilucent clouds over various time periods during their flights. The output correlated extremely well to the actual observations, giving the team confidence in their model.

Russell and his team will research further to determine if the noctilucent cloud frequency increase and accompanying temperature decrease over the 10 years could be due to a reduction in the sun’s energy and heat, which naturally occurred as the solar output went from solar maximum in 2002 to solar minimum in 2009.

“As the sun goes to solar minimum, the solar heating of the atmosphere decreases, and a cooling trend would be expected,” said Russell.

FRISCO — Forests may play a much bigger role in global climate than previously believed. In addition to cycling carbon, it appears that gases wafting from conifers quickly form small particles that can reflect sunlight and promote cloud formation, according to a new study that looked at forest aerosols at the molecular level.

“In many forested regions, you can go and observe particles apparently form from thin air. They’re not emitted from anything, they just appear,” said Joel Thornton, a University of Washington associate professor of atmospheric sciences. Continue reading →

Air pollution can have a significant impact on the development of thunderclouds, causing cloud remnants to persist longer. bberwyn photo.

FRISCO — Air pollution can have a significant effect on the development of thunderhead clouds, causing the cloud remnants to persist high in the atmosphere long after thunderstorms dissipate. This, in turn, can affect daily temperature ranges, as the lingering clouds partially cool the Earth during the day with their shadows, but trap heat to keep nighttime temperatures warmer.

The new study, from the Department of Energy’s Pacific Northwest National Laboratory, helps answer long-running questions about how airborne pollutants affect climate warming. The findings will help provide a gauge for the accuracy of weather and climate models.

“This study reconciles what we see in real life to what computer models show us,” said atmospheric scientist Jiwen Fan. “Observations consistently show taller and bigger anvil-shaped clouds in storm systems with pollution, but the models don’t always show stronger convection. Now we know why.” Continue reading →

New study suggests natural aerosols may be a bigger factor than previously thought

By Summit Voice

FRISCO — In their quest to better understand the role of aerosols in the Earth’s climate, researchers may have to try and find the cleanest parts of the atmosphere.

Knowing to what degree both human-caused and natural aerosols mask the effects of heat-trapping greenhouse gases is crucial to making accurate climate predictions, according to a new study that assessed 28 factors that could affect the uncertainties in cloud brightness.

Natural aerosols, such as emissions from volcanoes or plants, may contribute more uncertainty than previously thought to estimates of how the climate might respond to greenhouse gas emissions. Continue reading →

SUMMIT COUNTY — Airborne dust has been shown to speed up snowmelt in the Colorado Rockies, but there’s more to to global dust and snow story, according to a NOAA-led study showing that dust and microorganisms from as far away as the Sahara help spur the precipitation that California counts on for its water supply.

Heat building up over the Arctic is interfering with global circulation patterns, leading to more intense, frequent and extended extreme weather events. Diagram courtesy NOAA.

By Summit Voice

FRISCO — Increasing global temperatures are “freezing” atmospheric waves, resulting in more frequent weather extremes, including the 2011 U.S. heat wave and a 2010 heat wave in Russia that coincided with unprecedented flooding in Pakistan.

Scientists have surprised by how far outside past experience some of the recent extremes have been. The new data show that the emergence of extraordinary weather is not just a linear response to the mean warming trend.

“What we found is that during several recent extreme weather events these planetary waves almost freeze in their tracks for weeks,” said Vladimir Petoukhov, lead author of a study to be published this week in the US Proceedings of the National Academy of Sciences. “So instead of bringing in cool air after having brought warm air in before, the heat just stays. In fact, we observe a strong amplification of the usually weak, slowly moving component of these waves,” Petoukhov said. Continue reading →

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